In a conventional passenger vehicle, a conventional hydraulic brake system is essential. In addition, an anti-lock braking system (ABS) and an electronic stability program (ESP) can hydraulically brake a single or multiple wheels on the basis of the hydraulic brake system, so as to achieve an effect of speed reduction. However, when brake is necessary in the case of high speed driving, of taking turns or of avoiding obstacles abruptly, consequences would be unimaginable once brake of the systems fails.